Apparatus including a heated guide eye for winding a plurality of lengths of thermoplastic resin impregnated yarns

ABSTRACT

A consolidated structure with less than 6 percent void content is formed from a plurality of thermoplastic impregnated yarns traverse wound on a rotating mandrel by feeding the yarns under tension simultaneously from a source of supply to a traversing carriage as adjoining flat tapes. The tapes then move successively through a preheating section, a heated circular guide and a contact portion heating source, all on the carriage, before being laid down in a predetermined path on the mandrel.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of prior application Ser. No.07/370,587 filed Jun. 14, 1989, now abandoned, which in turn is acontinuation of prior application Ser. No. 07/095,235 filed Sep. 11,1987 and now abandoned.

BACKGROUND

This invention relates, to winding fiber-reinforced resin products, andmore particularly it relates to winding a plurality of lengths ofthermoplastic resin impregnated yarns to form an insitu consolidatedproduct.

Equipment for winding single length thermoplastic resin impregnated yarnon a mandrel is known. However, fabrication of parts in this manner isslow and costly because only one impregnated length of yarn is wound atlow speed. When scale-up has been attempted, the control of multiplelengths of such yarns during winding at higher speeds above 10 ft./min.presented barriers because heating the resin to its melt temperatureduring winding caused sticking of the polymer to guides, loss of controlof band width and fuzzing of the yarn. This resulted in unacceptableoperability as well as broken filaments which gave poor mechanicalproperties. In addition, the inability to get enough heat into amulti-end system to melt the polymer always produced parts with anunacceptable level of voids unless the product was subject to a postheating treatment. Furthermore, these limitations have deprived endusers of the lower cost improved products which could be obtained fromthermoplastic resin impregnated yarn.

SUMMARY OF THE INVENTION

According to the present invention, an insitu consolidated compositestructure (i.e., the ability to consolidate the structure during windingof the structure without the need of consolidation processing afterwinding) is built from a plurality of lengths of thermoplastic resinimpregnated yarns or tape wound simultaneously on a mandrel whereinmultiple ends of such yarns are fed at high speeds (above 10 ft./min.)under controlled tension in the range of 5% to 50% of the ultimatetensile strength of the yarn from a supply source to a traversingcarriage of a filament winder as a flat uniform tape. This tape thenmoves through the "head" portion of the filament winder containing apreheating section, a heated guide, and a contact point heating sourcebefore being laid down in a predetermined helical or geodesic path on arotating mandrel.

The head of the filament winder is mounted on the end of the carriagefeed arm which can move in and out compensating for changes incross-section of the rotating mandrel. Infra-red (IR) strip heaters aremounted on the head to preheat the multi-end impregnated yarn and aredesigned in length and intensity to bring thermoplastic resin to within±10° C. of its melt or processing temperature. The pre-heatedimpregnated yarn then passes across a heated guide that is maintained ata temperature above the melt temperature but below the degradationtemperature of the thermoplastic resin, and located as close as possibleto the surface of the part being wound. The heating of the guide iscritical to preventing polymer and fiber buildup on its surface at highspeeds of 25 ft./min. and above, and the location is critical tomaintaining impregnated yarn temperature until the impregnated yarnreaches the laydown point.

Mounted at the forward most portion of the head is a contact pointheating source which maintains the surface temperature of the part highenough, through induced heating of the mandrel and direct heating of thewound surface, to ensure molten mating surfaces at the laydown point ofthe incoming lengths of impregnated yarn. Hot air, open flame, and IRcontact point heating sources may be used. The selection of which sourceto use is dependent on the yarn, the thermoplastic resin, the mandreldesign, and operating speed.

Upon completion of the winding process all heat sources are removed andthe part is allowed to cool. After reaching room temperature the partmay easily be extracted from the mandrel and an insitu consolidated partwith less than 6% void content requiring no post-consolidation stepsresults.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of a winding apparatus for practicingthe invention.

FIG. 2 is a schematic side view of an alternate embodiment of FIG. 1.

FIG. 3 is a schematic side view of another embodiment of FIG. 1.

FIG. 4 is a side view of the head of the winding apparatus shownschematically in FIG. 1.

FIGS. 5 and 6 are side and front views respectively of the head of thewinding apparatus shown schematically in FIG. 2.

FIGS. 7 and 8 are front and side views, respectively, of an alternateheated guide useful in the apparatus of this invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

In FIGS. 1-3, the yarn-laying head used in practicing the invention isgenerally designated by the numberal 10 and is shown to include atraversing carriage 12 upon which is mounted a feed arm 14 movabletoward and away from a rotating mandrel 16. The traversing carriage,feed arm, and mandrel are a model W60-16 triple axis filament winderwith and N-210 computer by McClean Anderson of Milwaukee, Wis. Mountedto the feed arm 14 are infra-red heaters 18, i.e. a first heatingsource, a heated guide 20 , i.e. a second heating source, and an openflame heater 22, i.e. a third heating source (FIG. 1).

As carriage 12 is traversed longitudinally of mandrel 16 a plurality oflengths of thermoplastic resin impregnated yarns 24 are pulled from aplurality of supply packages 26 mounted on rolling takeoff creel 25against a desired level of back tension (in the range of 5% to 50% ofthe ultimate tensile strength of the tape) applied by a mechanism (notshown) associated with the creel for controlling unwind tension onpackages 26 such as a Type 800C012 tension compensator by CompensatingTension Controls, Inc., of West Caldwell, N.J.

As the yarn-laying head moves with respect to the structure being woundon mandrel 16, the thermoplastic resin impregnated lengths of yarn 24are exposed to radiant heaters 18 (model 5535 manufactured by ResearchInc. of Minneapolis, Minn.). In these heaters, the thermoplastic resinis heated to a temperature that is within 10° C. of its melttemperature. The lengths of yarn then pass through a heated guide 20which in the preferred embodiment is a circular eye made of aluminumwith a hard anodized finish coated with Teflon®. The guide is wrappedwith an electrically operated band heater 20a (such as an MI band heatermodel MBIEIJNI) which raises the temperature of the thermoplastic to atemperature above its melting point but below its degradationtemperature which should be understood to be below the melting point ofthe reinforcing fibers. Mounted at the forward end of feed arm 14 is anopen flame heater 22 (a Vulcan Universal propane torch with a No. 3 tip)over which the tapes 24 pass to the laydown location 28 on the mandrel16. This heater heats the surface of the part being wound on themandrel, through induced heating of the mandrel and direct heating oflengths of yarn 24 as they travel from the guide 20 to location 28 toensure molten mating surfaces at laydown location 28.

In FIG. 2, the third heating source, the open flame heater 22 isreplaced with an infra-red heater 22' (model 5535 by Research Inc.), andin FIG. 3 flame heater 22 is replaced with a hot air gun heater 22"(Serpentine VI model CHE128767 by Sylvania).

FIGS. 4, 5 and 6 show the physical relationship of the tapes, theheaters and heated guide on the head of the filament winder with respectto each other and the mandrel.

An alternate embodiment for guide 20 is shown in FIGS. 7 and 8. Moreparticularly, this guide 20' has a concave radiused surface 21 whichguides the tows 24 and embedded in the guide body 23 is a calrod heatingelement 20a'.

Void Content

To determine void content in a composite sample, the density of thesample must be measured and the density of a zero void sample must becalculated. From these two numbers, the void content of the sample canbe determined. Measurement of sample density: The density of the sampleswere measured using ASTM D 792-66 standard test method. The followingprocedures were followed:

1) Weigh sample in air (a)

2) Weigh sample in water (b)

3) Calculate the specific gravity (s.g.) of the sample s.g.=a/(a-b)

4) Calculate the density of the sample Measured density=s.g.×density ofwater at the measurement temperature.

Theoretical density for a sample with no voids:

    Dc=(Df×Vf)+(Dm×Vm)

where:

Dc=density of the composite

Df=density of the fiber

Dm=density of the matrix

Vf=fiber volume

Vm=matrix volume

Calculate the % void content: ##EQU1##

EXAMPLE I

A tow of Owen Corning's Type 30 continuous glass filaments havingapproximately 6620 denier and 2000 filaments is coated with PETGthermoplastic polymer (a copolymer manufactured by Eastman KodakCompany) using a melt-injection process (as described in U.S. Pat. No.4,640,861) to approximately 50% by volume coating level. Four bobbins ofthe coated tow of these glass filaments are mounted on a rollingtake-off creel equipped with a mechanism for controlling unwind tension(Type 800CO12 Tension Compensator made by Compensating Tension Controls,Inc.). The tow is advanced at 30 ft./min. by means of a rotating mandreldownstream and a tension of approximately 3500 gm is applied to themoving tow by the tension compensator. The moving tow passes through the"head" portion of the downstream filament winder which contains (1) apre-heating section (heated with an infrared heater) which heats the towto 260° C. followed by (2) a guide-eye which is preheated to 200° C.with bandheaters and (3) a hot air source which is positioned close tothe rotating mandrel (6 cm away) and maintains the temperature of thetow at 200 C. The tow is finally laid down on an electrically heatedmandrel (maintained at 250° C.). The computer controlled winder ispreprogrammed to provide a 12" long tube with 45° winding angle. Aftercompleting the winding, the mandrel and the tube are cooled forapproximately 1 hour until the temperature of the part is about 100° C.The wound tube is then removed, cut-up and tested for void content.

The filament winder used is a commercial winder made by McClean AndersonModel No. W-60 which was modified to adapt to this work as follows:

The thermoset resin bath was removed,

The thermoplastic head was mounted on the cross feed and power, waterand N2 was supplied to the carriage for a thermoplastic head.

The void content of the tube was 4.8%.

EXAMPLE II

A tow of Hercules AS4 continuous graphite filament having approximately3000 filaments is coated with a certain amorphous copolyamide polymer(as described in U.S. Pat. No. 4,681,411) using a melt-injection process(as described in U.S. Pat. No. 4,640,861) to approximately 50% by volumecoating level. Two bobbins of the coated tow of these graphite filamentsare mounted on two rolling take-off creels equipped with a mechanism forcontrolling unwind tension (Type 800C 012 Tension Compensator made byCompensating Tension Controls, Inc.). The tow is advanced at 25 ft./min.by means of a rotating mandrel downstream and a tension of approximately1500 gm is applied to each moving tow by the tension mechanism. Themoving tow passes through the "head" portion of the downstream filamentwinder which contains: (1) A pre-heating section (heated with aninfrared heater) which heats the tow to 320° C. following by, (2) Aguide eye which is preheated to 320° C. with band heaters and, (3) Aninfrared heating source which is positioned close to the rotatingmandrel 3 cm away) and maintains the temperature of the yarn at 320° C.(4) The tow is finally laid down on an electrically heated mandrel (at220° C).

Hot N2 (320°) was blown into the I.R. heat-up zone to reduce polymerdegradation. The computer controlled winder is preprogrammed to producea 6 ft long tube with +45°/+5°/90°/+45°/90°/+45°/90.degree. windingangles.

After completing the winding, the mandrel and the tube are cooled forapproximately 1 hour until the temperature of the part is about 100° C.The wound part is removed and tested for void content. The void contentwas 2.5%.

EXAMPLE III

A tow of Kevlar® 49 continuous filaments having approximately 1000filaments is coated with a certain amorphous copolyamide polymer (asdescribed in U.S. Pat. No. 4,681,411 using a melt-injection process (asdescribed in U.S. Pat. No. 4,640,861) to approximately 75% by volumecoating level.

Four bobbins of the coated tow of these Kevlar® 49 filaments are mountedon four rolling take-off creels equipped with a mechanism forcontrolling unwind tension (Type 800C 012 Tension Compensator made byCompensating Tension Controls, Inc.). The tow is advanced at 185ft./min. by means of a rotating mandrel downstream and a tension ofapproximately 1500 gm is applied to each moving tow by the tensionmechanism. The moving tow passes through the "head" portion of thedownstream filament winder which contains: (1) a pre-heating section(heated with an infrared heater) which heats the tow to 320° C. followedby, (2) a guide eye which is preheated to 325° C. with tank heaters and,(3) an open flame heater which is positioned close to the rotatingmandrel (3 inches away) and maintains the temperature of the yarn at320° C., and (4) the tow is finally laid down on a steel mandrel.

The computer controlled winder is preprogrammed to produce a 12 inchlong by 13.5 inch diameter part with all 90 wind angles.

After completing the winding, the mandrel and the tube are cooled forapproximately 1 hour until the temperature of the part is about 100° C.The wound part is removed and tested for void content. The void contentwas 2.2%.

What is claimed is:
 1. An apparatus for winding thermoplastic resinimpregnated yarns on a rotating mandrel at speeds of 25 ft./min. andabove comprising: a source of a plurality of said thermoplastic resinimpregnated yarns; means for tensioning said yarns; a carriage having acircular eye guide thereon through which said yarns pass for traversingsaid yarns back and forth on the mandrel to wind a product; anelectrically heated band heater wrapped around said guide to heat saidguide to a temperature above a melt temperature but below a degradationtemperature of said thermoplastic resin and means for maintaining thetemperature of said resin as said thermoplastic resin impregnated yarnspass from said guide until said yarns reach said mandrel whereby thethermoplastic resin does not stick to said guide and said yarn does notfuzz after passing through said guide at winding speeds of 25 ft./min.and above.